usb: gadget: configfs: Fix OOB read on empty string write

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: configfs: Fix OOB read on empty string write When writing an empty string to either 'qw_sign' or 'landingPage' sysfs attributes, the store functions attempt to access page[l - 1] before validating that the length 'l' is greater than zero. This patch fixes the vulnerability by adding a check at the beginning of os_desc_qw_sign_store() and webusb_landingPage_store() to handle the zero-length input case gracefully by returning immediately.

References

• https://git.kernel.org/stable/c/78b41148cfea2a3f04d87adf3a71b21735820a37
• https://git.kernel.org/stable/c/d68b7c8fefbaeae8f065b84e40cf64baf4cc0c76
• https://git.kernel.org/stable/c/15a87206879951712915c03c8952a73d6a74721e
• https://git.kernel.org/stable/c/2798111f8e504ac747cce911226135d50b8de468
• https://git.kernel.org/stable/c/58bdd5160184645771553ea732da5c2887fc9bd1
• https://git.kernel.org/stable/c/783ea37b237a9b524f1e5ca018ea17d772ee0ea0
• https://git.kernel.org/stable/c/22b7897c289cc25d99c603f5144096142a30d897
• https://git.kernel.org/stable/c/3014168731b7930300aab656085af784edc861f6